Jessica Allen didn't know what to think when her doctor told her she had moyamoya disease.

"It sounded like some exotic illness from another country," she recalls.

Moyamoya is in fact a very rare brain disorder. Its name originated across the ocean-in Japan-and the doctors capable of treating it are few and far between.

But Allen, a phlebotomist at University Hospital, was fortunate. The microsurgical procedure she needed was available at the Neuroscience Institute at UC and University Hospital.

Under the leadership of Mario Zuccarello, MD, the Neuroscience Institute is emerging as an important treatment center for patients suffering from moyamoya disease.

Zuccarello has surgically treated 29 patients with moyamoya during the last five years.

Moyamoya is characterized by a chronic and progressive narrowing of the carotid arteries where they enter the brain, causing debilitating strokes and seizures in patients.

The presence of moyamoya is confirmed by a series of imaging studies that can reveal the characteristic arterial narrowing. To compensate for the narrowing arteries, the brain creates collateral blood vessels in an attempt to facilitate the flow of oxygen-rich blood.

These tiny collateral vessels, when seen on a brain scan, have a hazy, filmy appearance-the "puff of smoke" that gives the disorder its Japanese name.

Allen was diagnosed with moyamoya in December 2007 by Matthew Flaherty, MD, assistant professor of neurology, after suffering her second stroke in four months. She had surgery in January.

The treatment for moyamoya, which is not widely offered, involves surgically bypassing the blocked arteries. In the most delicate and technically challenging bypass procedure, called an extracranial-intracranial bypass, Zuccarello connects the superficial temporal artery from the scalp outside the skull to the middle cerebral artery inside the skull.

"We are seeing more patients with moyamoya because patients and physicians are starting to recognize the disease more frequently and because the treatment, which requires highly specialized micro-vascular techniques, is available here at the Neuroscience Institute," says Zuccarello, a neurosurgeon with the Mayfield Clinic and director of the cerebrovascular surgery division at UC.

Although moyamoya disease is most prevalent in Japan, it has been diagnosed in people throughout the world.

In the United States, the disorder affects less than one in 100,000 people. However, the condition is associated with 6 percent of childhood strokes.

Because moyamoya disease runs in families, doctors believe the disorder has a genetic cause.

In children, symptoms of moya-moya are most likely to first appear with a transient ischemic attack (TIA) or ischemic stroke.TIAs are stroke-like symptoms that quickly resolve.

During an ischemic stroke, a blockage interrupts the flow of oxygen-carrying blood to the brain. In adults, the disease often appears with a TIA or hemorrhagic (bleeding) stroke.

"Moyamoya should be considered and diagnostic evaluation begun in any patient who experiences symptoms of cerebral ischemia," says Zuccarello.

Symptoms of ischemia may include episodes of muscle weakness or partial paralysis on one side of the body, speech disturbance, sensory impairment and visual impairment.

Doctors usually make a diagnosis of moyamoya if magnetic resonance images show diminished blood flow in the internal carotid and middle and anterior cerebral arteries, and prominent collateral blood flow at the base of the brain.

To confirm the diagnosis of moyamoya syndrome, conventional cerebral angiography is typically required.

For Allen, the surgical treatment was routine. She had a six-hour operation on a Thursday and went home the next day.